Modifications  

To begin with I'm NOT in favor of any permanent modifications to the drivers. No paints, lacers or butchery to the wizzer cone. Unless of course you're absolutely sure that the results will make the driver sound more to your liking. And never take this on faith. You must hear this for yourself. Keep in mind though that any permanent modifications to the driver can seriously reduce their resale value.

Modifications that are reversable are fine of course and below I've got one you may want to try. 


The $ 0.98 Mod.

This simple modification is 100% reversable and the material needed cost me only $ 0.98, hence the name. It's an attempt at attacking the resonance that occurs between the Lowther main and wizzer cone. There have been many suggestions in the past on how to combat this using wool or cotton stuffed behind the wizzer. While this does work it's hard to keep in the place that I think it needs to be. If you use the foam strip as shown below you can attack the problem more effectively and here's why:

The wizzer cone has no support on the outside. The main and the wizzer cone "excite" each other at certain frequencies and produce some nasty response peaks. It's no secret in loudspeaker design that a properly designed surround can do a lot to absorb resonances as they travel to the edge of the cone. Especially light ones ones like the Lowther that have to flex. Ted Jordan is really big on this. Of course the main cone has reasonable damping at it's outer edge by the foam surround.
And by the way it may that one of the reasons some of the older mid 1980's drivers didn't sound to swell was that the suspension was so stiff that there was in fact no "viscous" edge dampening of the main cone!?!?

Any way my idea was to ad a strip of light foam to the edge of the wizzer cone that connects it to the main cone "SOFTLY". This way resonances that are produced between the two are absorbed in the foam material. since the damping material as it were is placed only on the outside of the wizzer cone where it is needed it does not effect the wizzers operation as much. The critical area around the junction of the two cones remains unaffected. The mass inevitably added to the cone assembly is placed in a position were it has less effect on transient response at mid and higher frequencies.

So let's get started:

The foam I used was purchased a t a fabric store. It's 1/4 inch (6 mm ) thick and very light. One strip I weighed came in at 0.45 grams. Considering where it's placed I don't think that it should be enough of an increase in overall mass to cause major problems.
Now there are not years of R&D on this mod. I just came up with it recently but liked the results so here it is. There's probably plenty of fine tuning that could be done.

NOTE!!!:
Many people have tried this mod since it's been on this page and most like it very much. However some people found it did not work for them. Some investigation showed that they were using a different type of foam. Heavier basically. To make it as clear as possible the foam I used is very light, relatively soft and of a very "open" cell structure. If you had a large piece of the right stuff and held it up to your computer screen you would not be able to read this but you would be able to tell roughly where the icons on your screen are and be able to detect different colors through it. That should explain it.


 Making key measurements. 

Start by measuring the distance of the edge of the wizzer cone the the main cone at approximately the angle shown. Then cut a strip of the foam just a little bit wider, maybe 0.5 to 1 mm than the the measurement you just made and about 30 cm or so long. Cut as straight and evenly as you can. You may have to make several try's to get it right, but what the heck the stuff is cheap enough.

 
 
 
 
 
 

A little detail.


The object here is to get the foam to dampen the edge of the wizzer cone. NOT the junction of the two cones and voice coil. The drawing on the left should make this a bit clearer.
Insert the foam and stuff it evenly until it's just under the wizzer cone. The "angle" at which it touches the main cone cone s basically up to you and will depend to some degree on how thick you actually cut the strip.

 
 
 
 
 
 
 

Stuffing the foam.

Next start stuffing the foam in between the wizzer and main cone with your fingers as shown. If you've cut the strip correctly there will be slight interference fit with no or only little bulging of the foam. If the foam doesn't seem to fit well, to loose or not tight enough then cut a new one.
 
 
 

 
 
 
 
 
 
 

 


This is how it should look.

Continue stuffing the foam all the way around until you've reached your starting point. You can either mark the foam at the junction, remove and cut it or just "eye ball" it and cut to fit in place.

Either way the next step is to carefully tuck the foam strip in between the two cones so that the top edge is flush with the outside of the wizzer cone and mates to the main cone as shown in the photo. I use the eraser end of a pencil for this. Just keep working it until it fits nicely.

In actual use the foam may work it's way out a bit depending on how you cut and stuffed it. A small bead of glue may be in order here but ONLY on the foam were it meets. Not any where on the cones.

Drawbacks:
The only drawback I have found so far is that the foam doesn't keep it's shape for to long. It tends to loosen after a while in which case you need to re-stuff it or simply install a new piece. Maybe some one out there has some better material?
Email me with the info.

I'm currently working on a "pre-cut and glued" ring. Results are not in yet so stay tuned.


Now go ahead and have a listen. You may like it. You may not. It might appear as though some thing is "missing". Listen carefully...guess what it is.

One of the things I find most interesting is that with the drivers modified there is subtle increase in stereo sound stage or width.
I've thought about this and have only one possible answer for this phenomenon:

The inherent cone resonances that these drivers have are easily excited. That is to say that it does not necessarily require any specific frequency signal. So when playing music although many of signals the drivers receive are in fact different the resonances that are excited are the same. These are then heard as a mono signal!
Remove the resonances and you're left with more of the original stereo information not masked by the "mono" cone resonances.
Sort of makes sense doesn't it???

Now I'm not saying this is the cure all for the Lowthers resonance problem but I've been fairly happy with the results. And what's important is that it's reversible. At times there does seem to bit a bit of dulling on some transients and a very small loss of top end response...not a problem with my PM 2 A's. It may not work as well on some of the smaller models.

For example on Reference Recordings Three Way Mirror featuring Airto and flora Purim, on track one about half way through where you hear the.........ah what the hell, just go try it yourself.!!!
 
 
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